Psychology ETDs

Publication Date



A model was described that combines Grice's variable threshold model for reaction time and Logan's incentive theory for response speed in instrumental conditioning in an attempt to account for the relative performance of rats receiving continuous (CRF), varied (VRF), or partial (PRF) reinforcement. The essence of the model is that incentive motivation depends on the mean amount of reward previously received, as well as upon the S's distance from the goal, that incentive motivation can be interpreted as affecting the mean threshold for responding, and that the greater the variability in reward the greater the variability in the threshold.

This model generates a number of relative predictions, among which is that the performance of CRF, VRF, and PRF would be a function of magnitude of reward, stage in acquisition, and position in the runway. Also, the performance of CRF relative to PRF at one mean magnitude of reward dictates predictions concerning the relative performance of CRF and PRF conditions receiving greater or lesser mean magnitudes of reward. In addition, the model predicts that the goal gradients for CRF, VRF, and PRF would be equal at a point some distance from the goal, that this point of equality would move backward from the goal, and would be further away the larger the mean magnitude of reward. Other implications concern the effects of changing the conditions of reinforcement.

Degree Name


Level of Degree


Department Name


First Committee Member (Chair)

Frank Anderson Logan

Second Committee Member

G. Robert Grice

Third Committee Member

Douglas Peter Ferraro

Fourth Committee Member

Richard Jerome Harris



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Included in

Psychology Commons